Serotonin (5-HT) is a neurotransmitter distributed widely in the animal and vegetable kingdoms and has a broad spectrum of physiological actions. It is generally considered that there are three subtypes of serotonin receptors, viz. 5-HT.sub.1, 5-HT.sub.2 and 5-HT.sub.3.
Regarding the functions of 5-HT.sub.3 receptors, promotion of release of transmitters (noradrenalin, acetylcholine) from the nerves, depoloralization of the sympathetic and parasympathetic ganglions, reflex bradycardia and dolorogenesis are known. However, much remains to be elucidated about the functions of 5-HT.sub.3 receptors and the mechanisms of the antiemetic and psychotropic effects of its antagonists have not been established as yet. GR-38032F (ondansetron), a selective antagonist of 5-HT.sub.3 receptors, is said to markedly inhibit the emesis associated with the administration of anticancer drugs and, moreover, exhibit excellent anxiolytic and antipsychotic actions.
As indole derivatives having an azabicyclic group, a variety of compounds have heretofore been reported (e.g. Japanese Kokai Tokkyo Koho 63-277622, 63-277623, 62-116580 and 61-212521 and Japanese Patent Application 1-130899).
However, indole-3-carboxamide derivatives having a phenyl group in the 2-position of the indole nucleus have never been described in literatures so far nor are they included in the claims of any of the above-cited patent and pending patent literature.